Classification of Anthelmintic Drugs
Anthelmintic drugs are used to treat parasitic worm infections in humans. Here, we classify anthelmintics and describe each class's mechanism of action, therapeutic uses, adverse effects, and contraindications.
1. Benzimidazoles (e.g., Albendazole, Mebendazole)
Mechanism of Action
Benzimidazoles inhibit microtubule synthesis by binding to β-tubulin in parasites, which disrupts glucose uptake and energy production, leading to parasite death.
Therapeutic Uses
- Nematode infections: ascariasis, hookworm, trichuriasis, pinworm.
- Some cestodes: effective in neurocysticercosis.
Adverse Effects
- Gastrointestinal discomfort
- Rare hepatotoxicity
- Bone marrow suppression with prolonged use
Contraindications
- Pregnancy due to teratogenic risk
- Caution in liver disease
2. Avermectins (e.g., Ivermectin)
Mechanism of Action
Ivermectin binds to glutamate-gated chloride ion channels, causing paralysis and death of the parasite.
Therapeutic Uses
- Onchocerciasis (river blindness), strongyloidiasis, lymphatic filariasis
- Also effective in scabies and lice infestations
Adverse Effects
- Dizziness, headache, nausea
- Mazotti reaction in high parasite loads
Contraindications
- Children under five and pregnant women
- Patients with CNS disorders
3. Pyrantel Pamoate
Mechanism of Action
Works by causing spastic paralysis in worms through depolarizing neuromuscular blockade, facilitating expulsion by peristalsis.
Therapeutic Uses
- Effective against Ascaris, Enterobius (pinworm), and hookworms
Adverse Effects
- Nausea, vomiting, diarrhea
- Dizziness, headache
Contraindications
- Liver dysfunction
- Unclear safety in pregnancy
4. Praziquantel
Mechanism of Action
Increases cell membrane permeability to calcium, leading to parasite paralysis, dislodgment, and death.
Therapeutic Uses
- First-line treatment for trematodes (e.g., schistosomiasis) and cestodes (e.g., tapeworms)
Adverse Effects
- Abdominal discomfort, nausea, dizziness
- Transient increase in liver enzymes
Contraindications
- Caution in liver dysfunction
- Avoid in ocular cysticercosis to prevent inflammatory reactions
5. Diethylcarbamazine (DEC)
Mechanism of Action
Alters microfilariae surface structure, increasing susceptibility to the host’s immune system.
Therapeutic Uses
- Primarily used for filariasis and tropical eosinophilia
Adverse Effects
- Nausea, headache, joint pain
- Mazzotti reaction in onchocerciasis
Contraindications
- Caution in hypertension and renal impairment
- Avoid in onchocerciasis cases with eye lesions
